Lion and Time Machine local snapshots

Has anybody successfully used the new local snapshots feature of Time Machine?

It appears that you can enable the feature with the following command, which will create a hidden volume in /Volumes/MobileBackups:

Code:

sudo tmutil enablelocal

After doing this, I can "enter" Time Machine even when my external T.M. drive is disconnected. I can force the creation of snapshots with the command tmutil snapshot, and I can confirm from the command line that a snapshot was created in the hidden volume. However, if I try the following simple test, my results aren't promising:

Create a file or folder.

Force a snapshot with tmutil snapshot.

Delete the file.

When I enter Time Machine and look for the deleted file, it's nowhere to be found.

Well, here's another datapoint. I have a second Mac which was just upgraded to Lion, and on this machine, the MobileBackups volume is present without any explicit action on my part. And I can use the repro steps above to recover a deleted file from a local snapshot.

A difference between the two Macs which seems salient is that the first one had less than 10% free disk space, while the second has about 25% free disk space. So one hypothesis is that local snapshots are only enabled by default if the Mac has a certain amount of free disk space. And it's possible that this selective enablement is in place to guard against a bug that occurs when disk space is constrained. Of course, the problem I'm having on the first Mac might just be some weird thing that nobody else is seeing.

I don't have MobileBackups on my early-2006 MacBook, and the drive is sitting at 204GB of 499GB used. Perhaps that's because I did an upgrade install from 10.6.x to one of the developer previews, and from there, through another preview or two to the GM? /shrug

I have the volume. Late 2008 MBP, 32 of 250gb free. Clean install after Lion refused to install over my supposedly corrupt partition. Spent all day doing a fresh TM backup over Ethernet, not yet finished.